To swell a progress
In Hamlet, Rosencrantz, Guildenstern, Osric, and even Polonius aren’t tremendously significant figures in their own right. Prufrock thinks his destiny is similar. He may play a minor role in a larger story, or swell the numbers of a royal court, but he’s basically not a very big deal. He’s like an extra in a film or a hanger-on in an entourage.
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